What are examples to show Mickey and Edward’s personalities are more affected by nurture than nature?(blood brothers)?

On some level, the lives of Mickey and Edward seem almost like a science experiment: what will happen when two genetically similar boys are raised in vastly different circumstances? Is a person’s character determined more by their genetics, or by their upbringing? Throughout the play, Willy Russell illuminates the contrasts that stem from Mickey and Edward’s separate childhoods, and compares them with the similarities that the two share. Mickey, for instance, is rough, rebellious, and jaded from a young age. In contrast, Edward is intelligent but innocent, which is made clear by his generosity towards other children and his tendency to get himself in trouble by accident. The differences between the two boys are rooted in the fact that Mickey grew up in a rough and tumble neighborhood, while Edward came of age in the lap of luxury.
At the same time, however, the boys feel a kinship with each other, calling themselves “blood brothers” years before they know they are in fact related. Although they have many superficial differences, at core they are both loving, decent, and honest individuals, much like their mother, Mrs. Johnstone. Their similarities are further emphasized by the fact that they fall in love with the same woman, Linda, and she feels strongly about both of them. Tragically, it is ultimately this similarity that ultimately leads to their joint downfall. Russell never comes down on one side or the other in the “nature vs. nurture” argument, but instead shows how both genetics and upbringing affect one’s personality and fate.